Remote extensions cannot dail PSTN

I have a Thirdlane STE version 6.0.1.76 with a Digium t100p t1 card running asterisk 1.6.0.6. The problem that I am having is with remote extensions (phones outside the local network). Remote extensions can registrar fine and I can do extension to extension dialing but when I try and make a call to the t1 trunk it fails and I get
chan_sip.c:17107 handle_request_invite: Failed to authenticate user "503" from the asterisk CLI. I have tried multiple extensions and different hard phones (Polycom 550 and Snom 320) with the same results. The funny thing is that when I use Eye Beam softphone version 1.5.7 It works fine. I did a pcap trace on my Snom and received a 401 unauthorized and a 403 forbidden from the TL server. The server has private IP that has a one to one Nat behind a Visco 1720 router that is completely open.